Manufacturing of integrated circuits is generally a procedure of forming thin films and layers of various materials on wafers of base semiconductor material, and selectively removing areas of such films to provide structures and circuitry. Doped silicon is a typical base wafer material. There are a number of known processes for depositing layers in IC manufacturing, one of which is chemical vapor deposition (CVD).
CVD is a well-know way to deposit thin films and layers of materials that can be introduced to a process in a gaseous or vapor form. For example, polysilicon may be deposited from silane gas, SiH.sub.4. It is known, too, to deposit tungsten silicide from a mixture of gases including silane and a tungsten-bearing gas such as tungsten hexafluoride. Pure tungsten is also deposited on silicon wafers in the manufacture of integrated circuits, sometimes selectively and sometimes across the entire surface in a process known as "blanket" tungsten.
In a typical CVD process wafers are placed on supports within a sealable chamber, the chamber is sealed and evacuated, the wafers are heated, typically by heating the wafer support, and a gas mixture is introduced into the chamber. For example, in the blanket tungsten process, tungsten hexafluoride (WF.sub.6) and hydrogen are introduced as reactive gases and argon may be introduced as a non-reactive carrier gas. The (WF.sub.6) is the source of deposited tungsten.
Typically gases in a CVD process are flowed continuously during processing. The temperature of a substrate (wafer) to be coated is one of the variables that drives the chemical reaction to cause tungsten to be deposited on the wafer surface. It is important to control the temperature, the concentration of various gases in the mixture introduced, and such characteristics as the uniformity of flow of gas over the surface being coated, among other variables. An even thickness of a deposited layer is a critical characteristic.
Over the history of CVD processing a number of different sorts of CVD processes have been developed. In some processes a single atomic material is deposited, while in other processes a chemical combination of materials or a mixture of two or more materials may be deposited by introducing gases bearing the different materials.
In many CVD processes the chemistry is endothermic, and deposition is driven by added heat. In most cases the heat is added in the process by directly heating the substrate to be coated. In other processes a plasma is induced in the process chamber, and energy is added to drive the necessary chemistry by a high-frequency power supply.
Historically the many sorts of deposition processes that have been developed have led to highly individual and specialized deposition apparatus, such as processing chambers and apparatus for introducing energy and process gases. Equipment design has also evolved from single-chamber, single-substrate systems to batch processing systems capable of processing several substrates simultaneously, and finally to isolated single chamber processing stations served by robotic transfer apparatus through air locks and high vacuum transfer chambers, wherein a steady stream of substrates may be moved through a sequence of different processes. These latter systems, allowing isolated sequential processing of substrates are based on material handling equipment known in the art as cluster tools. It is to these later cluster tool designs to which the present invention pertains.
In the semiconductor equipment manufacturing industry at the time of the present patent application the design of cluster tools has been standardized to the point that modular components may be used from a variety of manufacturers in a single system. For example, a cluster tool transfer system manufactured by one supplier, may be adapted to deposition and conditioning processing stations manufactured by other suppliers. In this manner a very wide variety of processing stations has been developed.
This wide variety of processing stations available is not always an advantage. For example, when it becomes necessary to change the process or the order of processes in a cluster-tool-based system, it is conventionally necessary to completely remove and replace some or all of the processing stations adapted to a cluster tool transfer apparatus. This procedure of reestablishing the entire architecture of such a system is far from trivial, and requires a long and arduous sequence of tasks involving all of the power, gas feed and control connections, as well as physically replacing vacuum chambers and vacuum pumping apparatus.
What is clearly needed is a multipurpose processing chamber that provides a common platform to operate a broad variety of CVD and plasma-enhanced CVD processes, as well as conditioning processes such as dry etching. Such a multipurpose processing station is the subject of the disclosure and teachings of the present invention.